1. Field of the Invention
This invention relates to an adjustable tool to enable the stretch-wrap forming and joggling of a plurality of different workpieces by which to form a variety of contours therein. The invention has particular application in an aircraft production program which requires stretch-formed contours of extruded, roll-formed, or break-formed pieces of aluminum, and the like metals, in either of a tee, ell, or channel section.
2. Prior Art
As will be known to those skilled in the art, stretch-forming of aluminum extrusions to provide stringers for use in aircraft construction, or the like, has proven to be both a time consuming and relatively expensive procedure. More particularly, the conventional stretch-wrap forming technique commonly requires a relatively complex hard tooling process in which a particular die, or the like, is designed and constructed to fabricate each separate component part and, frequently, left and right-handed versions of the same part. A die is attached to a work surface and the workpiece is stretched over the die until permanent deformation occurs. The hard tooling system is typically fabricated to the net contour of the desired configuration with no allowance for springback. Inasmuch as springback is a consequence of all known stretch forming processes, parts formed to a net contour will generally not conform to the designed shape. When such non-conformance is beyond acceptable limits, additional expense and time delays are incurred, requiring either a modification in the processing sequence (i.e., forming the part both before and after an intermediate heat treatment step) or a reworking of the tool to compensate for springback.
Moreover, the cost to implement a conventional hard tooling system is typically the same, whether the system is used numerous times or a very few times. Hence, such considerations as described above make a conventional hard tooling system inefficient, inasmuch as a different hard tool may be required for each production part. Where a large number of different component parts is required for production, the cost and inconvenience (e.g. complexity, space consumption, and required workman skills) by which to implement a hard tooling system is undesirably maximized, especially when a different tool is required for each of the different parts.
Known to the prior art are various shaping devices having a plurality of movable members or clamping devices which adjustably interact with one another in a process for forming aircraft components, and the like. By way of example, U.S. Pat. No. 1,178,020 published Apr. 4, 1916, discloses a template in which heated spring stock is formed for shaping leaf springs.
U.S. Pat. No. 2,483,958 published Oct. 4, 1949, relates to a welding machine and means for guiding an automatic welding head along a welding path by means of a guide associated with a workpiece. U.S. Pat. No. 2,578,867 published Aug. 15, 1950, describes a method for manufacturing leaf springs by means of a hydraulically actuated bending machine that bends a heated spring assembly.
U.S. Pat. No. 3,616,676 published Nov. 2, 1971, discloses a jig device for bending ship plates by which the curvature of a resilient jig strap can be adjusted.
U.S. Pat. No. 3,868,102 published Feb. 25, 1975, describes a clamping device in which multiple, movable engaging elements are employed for applying clamping forces to flat and contoured objects.
Additional U.S. patents which generally describe adjustable clamping devices to interact with a workpiece are as follows:
______________________________________ U.S. Pat. No. Date Published ______________________________________ 1,321,895 November 18, 1919 2,549,002 April 17, 1951 2,754,708 July 17, 1956 ______________________________________
However, no patents are known in the prior art which show or suggest a stretch forming tool having an array of position-variable form blocks respectively connected to a plurality of elongated slots formed in a base plate, so that a workpiece can be stretch formed to any of a variety of different contours around the form blocks depending upon the positions of the form blocks in the respective slots.